Centrifugal-based microfluidic apparatus, method of fabricating the same, and method of testing samples using the microfluidic apparatus

ABSTRACT

Provided is a microfluidic apparatus including: a microfluidic structure for providing spaces for receiving a fluid and for forming channels, through which the fluid flows; and valves for controlling the flow of fluid through the channels in the microfluidic apparatus. The microfluidic structure includes: a sample chamber; a sample separation unit receiving the sample from the sample chamber and separating a supernatant from the sample by using a centrifugal force; a testing unit receiving the supernatant from the sample separation unit for detecting a specimen from the supernatant using an antigen-antibody reaction, and a quality control chamber for identifying reliability of the test.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Korean Patent Application No.10-2008-0096724, filed on Oct. 1, 2008 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND

1. Field

One or more embodiments relate to a microfluidic apparatus based on acentrifugal force, a method of fabricating the microfluidic apparatus,and a method of testing samples using the microfluidic apparatus.

2. Description of the Related Art

Examples of microfluidic structures of a microfluidic device include achamber which may accommodate a small amount of fluid, a channel throughwhich the fluid may flow, a valve which may adjust the flow of thefluid, and various functional units which may accommodate the fluid andconduct predetermined functions. A small chip on which the microfluidicstructures of a microfluidic device are mounted in order to performvarious tests including a biochemical reaction is referred to as abiochip, and in particular, a device which is formed to perform variousoperations in one chip is referred to as a lab-on-a-chip.

Driving pressure is required to transport a fluid within themicrofluidic structures of the microfluidic device, and a capillarypressure or a pressure provided by a pump is used as the drivingpressure. Recently, microfluidic devices using centrifugal force bymounting microfluidic structures in a disk-shaped platform have beenproposed. These devices are referred to as a lab-on-a-disk or a labcompact disk (CD).

SUMMARY

One or more embodiments include a microfluidic apparatus and a method oftesting samples using an antigen-antibody reaction.

One or more embodiments include a microfluidic apparatus based on acentrifugal force, for improving reliability of sample testingprocesses, and a method of testing samples.

One or more embodiments include a method of fabricating a microfluidicapparatus, which may easily fabricate a valve for controlling the flowof a fluid in a microfluidic structure.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented embodiments.

According to an aspect of one or more embodiments, there is provided amicrofluidic apparatus including: a microfluidic structure for providingspaces for receiving fluid and for forming channels, through which thefluid flows; and valves for controlling the flow of fluid through thechannels in the microfluidic apparatus, wherein the microfluidicstructure includes: a sample chamber; a sample separation unit receivingthe sample from the sample chamber and separating a supernatant from thesample using a centrifugal force; a buffer chamber receiving reactionbuffer; a washing buffer chamber receiving washing buffer; a reactionchamber connected to the sample separation unit, the buffer chamber, andthe washing buffer chamber, and coated with capture antibodies forcapturing a specimen; and a detection chamber connected to the reactionchamber for receiving a final reaction material, having a space in whichabsorbance is measured for testing the specimen.

The reaction chamber may include a reaction cartridge, on which thecapture antibodies and antigens are coated.

The microfluidic apparatus may further include: a first waste chamberreceiving impurities discarded from the reaction chamber; and a firstwaste channel connecting the reaction chamber to the first wastechamber, and having an end portion connected to the reaction chamber andtwo final ends that diverge from the end portion to be connected to thefirst waste chamber, wherein a closed valve and an open valve aredisposed on the end portion, and an open valve and a closed valve arerespectively disposed on the two final ends so that the reaction chamberand the first waste chamber are isolated from each other afterdiscarding the impurities twice from the reaction chamber.

The microfluidic apparatus may further include: a blank chamberproviding the detection chamber with a washing buffer for measuring areference absorbance; a second waste chamber receiving the washingbuffer discarded from the detection chamber; and a second waste channelconnecting the detection chamber to the second waste chamber, wherein aclosed valve and an open valve are disposed in the second waste channelso that the detection chamber and the second waste chamber are isolatedfrom each other after discarding the washing buffer.

The buffer chamber may include: a first buffer chamber receiving one ofa conjugate buffer for performing a sandwich immunoassay reaction and acompetitive protein for performing a competitive immunoassay reaction; asecond buffer chamber receiving a substrate buffer that represents apredetermined color due to a substrate reaction with a resultant of aconjugate reaction or the competitive immunoassay reaction; and a thirdbuffer chamber receiving a stop buffer that stops the substratereaction.

The microfluidic apparatus may further include: a vent chamber forming avent path which allows the buffer chamber to access external air,wherein closed valves are formed between the buffer chamber and the ventchamber and at an outlet of the buffer chamber.

The microfluidic apparatus may further include: a buffer meteringchamber for metering reaction buffer between the buffer chamber and thereaction chamber; and an excess buffer chamber receiving reaction bufferexceeding capacity of the buffer metering chamber.

The microfluidic apparatus may further include: a vent chamber forming avent path which allows the washing buffer chamber to access externalair, wherein closed valves are formed between the washing buffer chamberand the vent chamber and at an outlet of the washing buffer chamber.

The microfluidic apparatus may further include: a supernatant meteringchamber located between the sample separation unit and the reactionchamber to meter an amount of the supernatant.

The microfluidic apparatus may further include: a first quality control(QC) chamber located at a final end of the sample separation unit foridentifying whether the microfluidic apparatus is used or not bydetecting absorbance.

The microfluidic apparatus may further include: a second QC chamberconnected to the sample separation unit and receiving the sampleexceeding a capacity of the sample separation unit.

The microfluidic apparatus may further include: a third QC chamber fordetecting an absorbance of the supernatant, the third QC chamberconnected to a channel that connects the reaction chamber to the sampleseparation unit to receive the supernatant from the sample separationunit.

The microfluidic apparatus may further include: a fourth QC chamberreceiving a material, absorbance of which varies depending ontemperature.

The microfluidic apparatus may further include: a rotatable platform onwhich the microfluidic structure is formed. The platform may include apartition plate, on which an engraved structure providing spaces forreceiving the fluid and for forming channels through which the fluidflows and having an opened upper portion is formed, and an upper platecoupled to the upper portion of the partition plate to block the upperportion of the engraved structure.

The valves may include a valve material that is melted byelectromagnetic wave energy. The valve material may be a phasetransition material, a phase of which is changed by the electromagneticwave energy, or a thermosetting resin. The valve material may includefine heating particles dispersed in the phase transition material togenerate heat by absorbing the electromagnetic wave energy.

According to another aspect of one or more embodiments, there isprovided a microfluidic apparatus including: a microfluidic structurefor providing spaces for receiving fluid and for forming channelsthrough which the fluid flows; and valves for controlling the flow offluid through the channels in the microfluidic structure, wherein themicrofluidic structure includes: a sample chamber; a sample separationunit receiving the sample from the sample chamber and separating asupernatant from the sample by using a centrifugal force; a testing unitincluding a detection chamber, in which a resultant of anantigen-antibody reaction between the supernatant, capture antibody orcapture antigen, and a reaction buffer is received; and a QC chamber foridentifying reliability in specimen detection.

The QC chamber may include a first QC chamber located at a final end ofthe sample separation unit for identifying whether the microfluidicapparatus is used or not by detecting absorbance.

The microfluidic apparatus may further include: a second QC chamberconnected to the sample separation unit, receiving the sample exceedinga capacity of the sample separation unit.

The microfluidic apparatus may further include: a third QC chamberconnected to a channel that connects the reaction chamber to the sampleseparation unit to detect a state of the supernatant.

The microfluidic apparatus may further include: a fourth QC chamberreceiving a material, absorbance of which varies depending ontemperature.

The microfluidic apparatus may further include: a rotatable platform onwhich the microfluidic structure is formed. The detection chamber andthe QC chamber may be located at the same distances from a center ofrotation in a radial direction of the platform. The platform may includea partition plate, on which an engraved structure providing spaces forreceiving the fluid and for forming channels through which the fluidflows and having an opened upper portion is formed, and an upper platecoupled to the upper portion of the partition plate to block the upperportion of the engraved structure. The upper plate may include aprotective unit for protecting regions corresponding to the detectionchamber and the QC chamber from being contaminated. The protective unitmay include ribs surrounding the regions corresponding to the detectionchamber and the QC chamber.

According to another aspect of one or more embodiments, there isprovided a microfluidic apparatus including: a microfluidic structurefor providing spaces for receiving fluid and for forming channelsthrough which the fluid flows; and valves for controlling the flow offluid through the channels in the microfluidic structure, wherein themicrofluidic structure includes: a sample chamber; a sample separationunit receiving the sample from the sample chamber and separating asupernatant from the sample by using a centrifugal force; a testing unitincluding a detection chamber, in which a resultant of anantigen-antibody reaction between the supernatant, the capture antibody,and reaction buffer is received; and a temperature detection chamberincluding a material, absorbance of which varies depending ontemperature.

According to another aspect of one or more embodiments, there isprovided a method of fabricating a microfluidic apparatus, the methodincluding: preparing a partition plate including an engraved structurewhich provides spaces for receiving fluid and channels through which thefluid flows and includes an open upper portion; preparing an upperplate; applying a valve material onto a plurality of locations, wherevalves control the flow of fluid through the channels, of a lowersurface of the upper plate; coupling the upper plate to the partitionplate to block the open upper portion, and forming a plurality of openvalves; and forming a closed valve by applying energy to at least one ofthe plurality of open valves to melt the valve material and block thechannel.

The valve material may be melted by electromagnetic wave energy. Thevalve material may be a phase transition material, a phase of which ischanged by the electromagnetic wave energy, or a thermosetting resin.The valve material may include fine heating particles dispersed in thephase transition material to generate heat by absorbing theelectromagnetic wave energy.

According to another aspect of one or more embodiments, there isprovided a method of testing a specimen, which tests specimens includedin a sample by separating a supernatant from the sample, performing anantigen-antibody reaction between the supernatant and a reaction buffer,and receiving a resultant of the reaction in a detection chamber andmeasuring absorbance of the resultant using a microfluidic apparatusincluding a sample chamber, a sample separation unit, and a testingunit, and receiving the reaction buffer and a washing buffer, the methodincluding: loading the sample into the sample chamber of themicrofluidic apparatus; mounting the microfluidic apparatus onto arotation driver; and determining whether the microfluidic apparatus isalready used or not by measuring an absorbance of a first QC chamberthat is located at an end portion of the sample separation unit by usinga detector.

The method may further include: conveying the sample from the samplechamber to the sample separation unit by a centrifugal force that isgenerated by the microfluidic apparatus rotated using the rotationdriver; and determining whether an amount of the sample is sufficient ornot by measuring absorbance of a second QC chamber which receives thesample exceeding the capacity of the sample separation unit using thedetector.

The method may further include: determining whether a temperature of themicrofluidic apparatus is appropriate for starting the test by measuringabsorbance of a fourth QC chamber, the absorbance of which variesdepending on the temperature, by using the detector.

The method may further include: centrifugating the supernatant from thesample received in the sample separation unit by rotating themicrofluidic apparatus by using the rotation driver; conveying thesupernatant to the testing unit; measuring absorbance of a third QCchamber that diverges from a channel connecting the sample separationunit to the testing unit by using the detector; and determining whetherthe amount of supernatant is sufficient, whether a state of thesupernatant is suitable for the test, or whether a valve located betweenthe sample separation unit and the testing unit is defective, based onthe measured absorbance.

The method may further include: performing the antigen-antibody reactionbetween the supernatant, capture antibody, and the reaction buffer in areaction chamber to form the reaction resultant; determining a referenceabsorbance by measuring the absorbance of the detection chamber;conveying the reaction resultant to the detection chamber and measuringthe absorbance of the detection chamber; and calculating a concentrationof the specimen from a difference between the reference absorbance andthe measured absorbance. The measuring of the reference absorbance mayinclude supplying the washing buffer to the detection chamber andmeasuring the absorbance of the detection chamber.

The method may further include: obtaining information regarding at leastone of a fabrication date of the microfluidic apparatus, a term ofvalidity of the microfluidic apparatus, and a relation between themeasured absorbance and the concentration of the specimen from a barcodeformed on a side portion of the microfluidic apparatus, by using abarcode reader.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings of which:

FIG. 1 is a plan view of a microfluidic apparatus according to anembodiment;

FIG. 2A is a detail view of a testing unit included in the microfluidicapparatus of FIG. 1;

FIG. 2B is a detail view of a sample chamber included in themicrofluidic apparatus of FIG. 1;

FIG. 2C is a detail view of a sample separation unit included in themicrofluidic apparatus of FIG. 1;

FIG. 2D is a detail view of a first buffer chamber included in themicrofluidic apparatus of FIG. 1;

FIGS. 3A and 3B are cross-sectional views showing a reaction cartridgecoupling to a platform in the microfluidic apparatus of FIG. 1;

FIGS. 4A and 4B are cross-sectional views showing operations of a closedvalve in the microfluidic apparatus of FIG. 1;

FIGS. 5A and 5B are cross-sectional views showing operations of an openvalve in the microfluidic apparatus of FIG. 1;

FIG. 6 is an exploded perspective view of the microfluidic apparatus ofFIG. 1;

FIG. 7 is an exploded perspective view illustrating processes of formingthe closed valve and the open valve in the microfluidic apparatus ofFIG. 1;

FIG. 8A is a cross-sectional view of the open valve fabricated by theprocesses illustrated in FIG. 7;

FIG. 8B is a cross-sectional view of the closed valve fabricated by theprocesses illustrated in FIG. 7;

FIG. 8C is a cross-sectional view showing opening of the closed valveshown in FIG. 8B;

FIG. 8D is a view showing an example of a microfluidic apparatusadopting the valve fabricated by the processes illustrated in FIG. 7;

FIG. 9 is a perspective view of the microfluidic apparatus of FIG. 1;and

FIG. 10 is a diagram of an example of a sample analyzing system.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings, wherein like referencenumerals refer to the like elements throughout. In this regard, thepresent embodiments may have different forms and should not be construedas being limited to the descriptions set forth herein. Accordingly, theembodiments are merely described below, by referring to the figures, toexplain aspects of the present description.

FIG. 1 is a plan view of a microfluidic apparatus according to anembodiment; and FIG. 2A is a detail view of a microfluidic structureshown in FIG. 1. The microfluidic apparatus based on a centrifugal forceaccording to the present embodiment may include a platform 100 that is arotatable disk. The platform 100 includes a space for receiving a fluid,and a microfluidic structure for providing a fluid path. The platform100 is not limited to the disk shape. The platform 100 may be formed ofa plastic material such as acryl or polydimethylsiloxane (PDMS) whichmay be molded easily and has a biologically inert surface. However, thepresent embodiment is not limited to the above example, and the platform100 may be formed of a material having chemical and biologicalstability, optical transparency, and mechanical processability. Theplatform 100 may include a plurality of plates. An engraved structurecorresponding to a chamber or a channel is formed in a surface of aplate, which faces another plate, and then, the plates are bonded toeach other to provide a space for receiving the fluid and the fluid pathin the platform 100. The bonding of the plates may be performed using anadhesive or a dual-adhesive tape, ultrasonic wave, or laser.

The platform 100 may include one or more microfluidic structures. Forexample, the platform 100 may be divided into a plurality of regions,and a microfluidic structure which operates independently may beinstalled in each of the regions. According to the microfluidicapparatus of the present embodiment, the microfluidic structures arerespectively installed on two regions 101 and 102 of the platform 100 todetect specimens from a sample, for example, blood, through anantigen-antibody reaction. Since the microfluidic structures installedin the two regions 101 and 102 are substantially the same as each otherexcept for the specimens to be detected, the microfluidic structureinstalled in the region 101 will be described in more detail.

Referring to FIG. 2A, a sample chamber 10, a sample separation unit 30,and a testing unit 20 are formed. The sample chamber 10 provides a spacefor receiving a liquid sample, for example, blood. The sample separationunit 30 performs centrifugation to divide the sample into a supernatant(for example, blood serum or blood plasma) and a precipitate (forexample, blood cells). The testing unit 20 is a structure for detectingcertain protein included in the supernatant using the antigen-antibodyreaction, for example, detecting prostate specific antigen (PSA) andtestosterone for detecting prostate cancer, or detecting thyroidstimulating hormone (TSH) or free T4 (fT4) protein for testing thyroiddisease. The testing unit 20 of the present embodiment may detect theprotein using a sandwich immunoassay method or a competitive immunoassymethod.

FIG. 2B shows the sample chamber 10 in detail. Referring to FIG. 2B, thesample chamber 10 includes an inlet 11 for injecting samples, and areceiving portion 12 for receiving the sample. The receiving portion 12includes an outlet 13 connected to the sample separation unit 30. Theoutlet 13 may form a capillary pressure so that the sample may not moveto the sample separation unit 30 when the centrifugal force is notapplied, as will be described later. The outlet 13 may include a valvefor controlling the flow of the sample. In addition, in order to easilyinduce the samples received in the receiving portion 12 by thecentrifugal force into the sample separation unit 30, a side wall 19 athat is located farther from a center C between two side walls 19 a and19 b in a radial direction of the receiving portion 12 is formed so thata distance from the center C may increase from the inlet 11 to theoutlet 13. A structure, which makes the sample flow to the receivingportion 12 due to an injection pressure of the sample and prevents thesample reaching the receiving portion 12 from returning to the inlet 11,that is, a structure performing as a capillary valve that passes thesample only when a pressure of a predetermined level is applied, may beformed between the inlet 11 and the receiving portion 12.

A backflow prevention unit 14 may be disposed in the receiving portion12 in a direction crossing a flowing direction of the sample which flowsfrom the inlet 12 to the outlet 13. The backflow prevention unit 14 maybe formed as one or more ribs. The backflow prevention unit 14 acts as aflow resistance to the sample so that the sample is prevented fromflowing from the receiving portion 12 to the inlet 11.

The sample is conveyed from the sample chamber 10 to the sampleseparation unit 30 by the centrifugal force generated by the rotation ofthe platform 100, and thus, the sample separation unit 30 is located onan outer portion of the sample chamber 10. The sample separation unit 30for centrifugating the sample may be formed in various shapes, and anexample of the sample separation unit 30 is shown in FIG. 2C in detail.Referring to FIG. 2C, the sample separation unit 30 includes asupernatant collecting unit 31 formed as a channel extending radiallyfrom the sample chamber 10 toward the outside, and a precipitatecollecting unit 32 located at an end portion of the supernatantcollecting unit 31 to provide a space for collecting precipitates of alarge specific gravity. The supernatant collecting unit 31 includes asample distributing channel 34 for distributing the supernatant to thetesting unit 20. A valve 33 controls the flow of the sample through thesample distributing channel 34. Various types of microfluidic valves maybe adopted as the valve 33. The valve 33 of the present embodiment is anormally closed valve that closes the channel 34 so as to not allow thefluid to flow, before being opened due to an external power source.Referring to FIG. 2C, a plurality of stepped portions 31 a may be formedin the supernatant collecting unit 31. The plurality of stepped portions31 a may denote a separation level of, for example, serum. The pluralityof stepped portions 31 a may represent separation levels of 40%, 35%,32%, 30%, and 28% from the bottom. The separation level may be anelement for checking the state of blood taken from a patient or a healthcondition of the patient.

Next, the testing unit 20 will be described in detail. Referring to FIG.2A, a supernatant metering chamber 40, a reaction chamber 200, first,second, and third buffer chambers 210, 220, and 230, a washing bufferchamber 240, and a detection chamber 250 are shown.

The supernatant metering chamber 40 for metering an amount of thesupernatant may be disposed between the sample separation unit 30 andthe testing unit 20. The supernatant metering chamber 40 has an internalspace that may receive the amount of supernatant used in the testing.The supernatant metering chamber 40 includes a valve 41 for controllingthe flow of fluid on an outlet thereof. The valve 41 is a normallyclosed valve, like the valve 33. The supernatant metering chamber 40 isconnected to the testing unit 20 through a channel 42.

The first, second, and third buffer chambers 210, 220, and 230 receive areaction buffer used in the antigen-antibody reaction.

FIG. 2D shows a peripheral structure of the buffer chamber 210 indetail. Referring to FIG. 2D, the first buffer chamber 210 receives afirst buffer. The first buffer may be a conjugate buffer for performingsandwich immunoassay or may include a competitive protein for performingcompetitive immunoassy. The first buffer chamber 210 is connected to afirst vent chamber 215. The first vent chamber 215 forms a vent pathwhich allows the first buffer chamber 210 to access external air so thatthe first buffer received in the first buffer chamber 210 may bedischarged easily. A valve 212 is disposed between the first bufferchamber 210 and the first vent chamber 215. A valve 213 is disposed atan outlet of the first buffer chamber 210. The valves 212 and 213 arenormally closed valves. The first buffer is loaded into the first bufferchamber 210 and the valves 212 and 213 are installed, and then, thefirst buffer chamber 210 is maintained in the closed state beforeopening the valves 212 and 213. A first metering chamber 211 is forsupplying a fixed amount of first buffer that is used in the testing, tothe reaction chamber 200. The first metering chamber 211 is connected tothe first buffer chamber 210 through the valve 213. A valve 214 isdisposed in an outlet of the first metering chamber 211. The valve 214is normally closed. When the valve 214 opens, the first buffer that ismetered by the first metering chamber 211 may be supplied to thereaction chamber 200.

A peripheral structure around the second buffer chamber 220, the thirdbuffer chamber 230, and the washing buffer chamber 240 is similar tothat of the first buffer chamber 210. Referring to FIG. 2A, the secondbuffer chamber 220 receives a second buffer. The second buffer may be asubstrate buffer that represents a predetermined color due to asubstrate reaction with a resultant of the conjugate reaction or thecompetitive reaction. The second buffer chamber 220 is connected to asecond vent chamber 225. The second vent chamber 225 forms a vent paththat allows the second buffer chamber 220 to access the external air sothat the second buffer received in the second buffer chamber 210 may bedischarged easily. A valve 222 is disposed between the second bufferchamber 220 and the second vent chamber 225. A valve 223 is disposed inan outlet of the second buffer chamber 220. The valves 222 and 223 arenormally closed. The second buffer is loaded into the second bufferchamber 220 and the valves 222 and 223 are installed, and then, thesecond buffer chamber 220 maintains the closed state before opening thevalves 222 and 223. A second metering chamber 221 is for supplying afixed amount of the second buffer that is used in the testing to thereaction chamber 200. The second metering chamber 221 is connected tothe second buffer chamber 220 through the valve 223. A valve 224 isdisposed at an outlet of the second metering chamber 221. The valve 224is the normally closed valve. When the valve 224 opens, the secondbuffer metered by the second metering chamber 221 may be supplied to thereaction chamber 200.

A first excessive buffer chamber 229 is connected to the first andsecond metering chambers 211 and 221. Portions of the first and secondbuffers exceeding the capacities of the first and second meteringchambers 211 and 221 are received in the first excess buffer chamber229.

The third buffer chamber 230 receives a third buffer. The third buffermay be a buffer for stopping the substrate reaction, that is, a stopsolution. The third buffer chamber 230 is connected to a third ventchamber 235. The third vent chamber 235 forms a vent path that allowsthe third buffer chamber 230 to access the external air_so that thethird buffer received in the third buffer chamber 230 may be dischargedeasily. A valve 232 is disposed between the third buffer chamber 230 andthe third vent chamber 235. A valve 233 is disposed at an outlet of thethird buffer chamber 230. The valves 232 and 233 are normally closed.The third buffer is loaded into the third buffer chamber 230 and thevalves 232 and 233 are installed, and then, the third buffer chamber 230is maintained in the closed state before opening the valves 232 and 233.A third metering chamber 231 is for supplying the fixed amount of thirdbuffer that is used in the testing to the reaction chamber 200. Thethird metering chamber 231 is connected to the third buffer chamber 230through the valve 233. A valve 234 is disposed in an outlet of the thirdmetering chamber 231. The valve 234 is normally closed. When the valve234 opens, the fixed amount of third buffer that is metered by the thirdmetering chamber 231 may be supplied to the reaction chamber 200.

A second excess buffer chamber 239 is connected to the third meteringchamber 231. The third buffer exceeding the capacity of the thirdmetering chamber 231 is received in the second excess buffer chamber239.

The washing buffer chamber 240 may receive a washing buffer which washesaway residuals after performing the antigen-antibody reaction. Thewashing buffer chamber 240 is connected to a fourth vent chamber 245.The fourth vent chamber 245 forms a vent path that allows the washingbuffer chamber 240 to access the external air so that the washing bufferreceived in the washing buffer chamber 240 may be discharge easily. Avalve 242 is disposed between the washing buffer chamber 240 and thefourth vent chamber 245. The washing buffer chamber 240 is connected tothe reaction chamber 200 through a valve 243. The valves 242 and 243 arenormally closed. In addition, the washing buffer chamber 240 may beconnected to a blank chamber 241 through a valve 244. The blank chamber241 may be connected to the detection chamber 250 through a valve 246.The valve 244 is normally open. The open valve closes a channel byreceiving a driving power from the outside, and opens the channel beforereceiving the driving power so that the fluid may flow. Therefore, thewashing buffer is received in the washing buffer chamber 240 and theblank chamber 241. The valve 246 is normally closed. The washing bufferis loaded into the washing buffer chamber 240 and the valves 242, 243,and 246 are installed, and then, the washing buffer chamber 240 ismaintained in the closed state before opening the valves 242, 243, and246.

The reaction chamber 200 receives the supernatant from the supernatantmetering chamber 40 through a channel 42. The reaction chamber 200includes capture antibodies or capture antigens for performing theantigen-antibody reaction with the sample. For example, the reactionchamber 200 may be formed by coupling a reaction cartridge 201 coatedwith capture antibodies to a mounting portion 202 installed in theplatform 100 as shown in FIG. 3A. The reaction cartridge 201 may becoupled to the platform 100 by using various methods such as ultrasonicwave fusion, hot-melt bonding, or laser bonding. Reference numeral 203denotes a fusion protrusion. For example, when the ultrasonic wavefusion is performed, the fusion protrusion 203 is melted by theultrasonic wave energy and hardened so that the reaction cartridge 201is coupled to the platform 100. The fusion protrusion 203 may bedisposed on side portions of the reaction cartridge 201.

A first waste chamber 260 receives impurities discarded from thereaction chamber 200. An end 261 of a first waste channel 264 isconnected to the reaction chamber 200, and two final portions 262 and263 of the first waste channel 264 diverge from the end 261 and areconnected to the first waste chamber 260. Valves 205 and 206 aredisposed at the end portion 261 of the first waste channel 264, and avalve 265 and a valve 266 are respectively disposed at the two finalportions 262 and 263. The valves 205 and 266 are the normally closedvalves, and the valves 206 and 265 are the normally open valves.

The detection chamber 250 is connected to the reaction chamber 200through a valve 207, and receives the final fluid, the reaction of whichis finished, from the reaction chamber 200. In addition, as describedabove, the detection chamber 250 is connected to the blank chamber 241to be provided with the washing buffer.

A second waste chamber 270 is connected to the detection chamber 250through a second waste channel 271. Valves 251 and 272 are formed in thesecond waste channel 271. The valve 251 is the normally closed valve,and the valve 272 is the normally open valve.

Referring to FIG. 2A, quality control (QC) chambers, which ensurereliability of the sample analysis, will now be described.

A first QC chamber 35 is disposed at an end portion of the sampleseparation unit 30 for detecting whether the microfluidic apparatus hasbeen previously used. Before supplying the sample from the samplechamber 10 to the sample separation unit 30, an absorbance of the firstQC chamber 35 is measured using a detector (520 of FIG. 10) that will bedescribed later so as to check whether the sample is in the first QCchamber 35, and thus, it may be detected whether the microfluidicapparatus has been previously used.

A second QC chamber 50 is provided to identify whether a sufficientamount of sample used to perform the testing is supplied to the sampleseparation unit 30. The second QC chamber 50 is connected to an upperend of the sample separation unit 30 through a channel 51. A portion ofthe sample exceeding the capacity of the sample separation unit 30 ismoved to the second QC chamber 50 through the channel 51. Aftersupplying the sample from the sample chamber 10 to the sample separationunit 30 and before performing the centrifugating operation, absorbanceof the second QC chamber 50 is measured using the detector (520 of FIG.10) to check whether the sample is in the second QC chamber 50, andthus, it may be checked whether the sample is supplied in the amountrequired to the sample separation unit 30.

A third QC chamber 60 is provided to identify whether the centrifugationby the sample separation unit 30 is appropriately performed. The thirdQC chamber 60 is connected to the supernatant collecting unit 31 of thesample separation unit 30 through the sample distributing channel 34 anda channel 61. When the valve 33 is opened, the supernatant fills thethird QC chamber 60. Absorbance of the third QC chamber 60 is measuredusing the detector (520 of FIG. 10). When the measured absorbancerepresents a reference absorbance that denotes that the supernatantsufficiently fills the third QC chamber 60, it implies that thecentrifugation performed by the sample separation unit 30 is normallyperformed. When the measured absorbance is greater than the referenceabsorbance, the centrifugation of the sample is not performed normallyand impurities are included in the supernatant or the sample isdefective. In addition, when the third QC chamber 60 is not completelyfilled with the supernatant, the supernatant may include air pores, andin this case, the absorbance is greater than the reference absorbance.Therefore, the lack of the supernatant may be identified. In addition,the operation of the valve 33 may be identified by measuring theabsorbance of the third QC chamber 60. That is, when the measuredabsorbance denotes the empty state of the third QC chamber 60, itimplies that the valve 33 does not operate properly. A valve 62 may bedisposed in the channel 61. The valve 62 is the normally closed valve.The valve 62 may be opened after the supernatant is moved to thesupernatant metering chamber 40 when the valve 33 is opened.

A fourth QC chamber 70 is a temperature detection chamber for detectingwhether a temperature of the sample is appropriate for the testing. Todo this, a material whose absorbance varies according to the temperaturemay be loaded into the fourth QC chamber 70. For example, thyon dye maybe loaded into the fourth QC chamber 70. The absorbance of the fourth QCchamber 70 is measured using the detector (520 of FIG. 10) to identifywhether the temperature of the microfluidic apparatus is appropriate forperforming the testing.

The washing buffer is loaded into the detection chamber 250 through theblank chamber 241 in order to check the state of the detection chamber250. Contamination of the detection chamber 250 affects the detection ofthe final absorbance. A chamber (not shown) may be formed besides thedetection chamber 250 and absorbance of this chamber may be used as thereference absorbance. However, in this case, the normal absorbance isnot the absorbance of the detection chamber 250, in which the testing isactually performed, and thus, the reference absorbance does not denotethe state of the detection chamber 250. In the present embodiment, afixed amount of washing buffer is loaded into the detection chamber 250,and after that, the absorbance is measured using the detector (520 ofFIG. 10). This measured absorbance becomes the reference absorbance thatrepresents the state of the detection chamber 250. After discarding thewashing buffer, the final fluid, the reaction of which is finished, issupplied from the reaction chamber 200 to the detection chamber 250 andthe absorbance of the fluid is measured, and then, a difference betweenthe measured absorbance and the reference absorbance may prevent theabsorbance detection error that may be caused by the state of thedetection chamber 250 which varies depending on the manufacturing statusof the microfluidic apparatus.

The first to fourth QC chambers 35, 50, 60, and 70 may be located at thesame distance in a radial direction from the center C in order tominimize the movement of the detector (520 of FIG. 10).

The normally closed valve and the normally open valve will be describedin detail. The normally open valve and the normally closed valve arevalves which operate actively by receiving a driving power or energyfrom the outside. Hereinafter, operating principles of the normallyclosed valve and the normally open valve will be described, andprocesses of fabricating the valves will be described later.

FIGS. 4A and 4B are cross-sectional views showing an example of thenormally closed valve adopted in the microfluidic apparatus of FIG. 1.The normally closed valve may include a valve material V1 that is solidat room temperature. The valve material V1 exists in the channel C in asolid state to block the channel C as shown in FIG. 4A. The valvematerial V1 is melted at a high temperature and is moved in a space inthe channel C, and then, coagulates while opening the channel C as shownin FIG. 4B. The energy irradiated from the outside may beelectromagnetic waves, and an energy source may be a laser light sourceirradiating laser beams or a light emitting diode or a Xenon lampirradiating visible rays or infrared rays. When the energy source is thelaser light source, the energy source may include at least one laserdiode. The external energy source may be selected according to awavelength of the electromagnetic wave, which may be absorbed by aheating element included in the valve material V1. The valve material V1may be a thermoplastic resin such as cyclic olefin copolymer (COC),polymethylmethacrylate (PMMA), polycarbonate (PC), polystyrene (PS),polyoxymethylene (POM), perfluoralkoxy (PFA), polyvinylchloride (PVC),polypropylene (PP), polyethylene terephthalate (PET),polyetheretherketone (PEEK), polyamide (PA), polysulfone (PSU), andpolyvinylidene fluoride (PVDF). In addition, a phase transition materialthat is in the solid state in the room temperature may be used as thevalve material V1. The phase transition material may be wax. When thewax is heated, the wax is melted to a liquid state, and a volume of thewax increases. The wax may be paraffin wax, microcrystalline wax,synthetic wax, or natural wax. The phase transition material may be agel or a thermoplastic resin. The gel may be polyacrylamide,polyacrylates, polymethacrylates, or polyvinylamides. In the valvematerial V1, a plurality of fine heating particles which absorb theelectromagnetic wave energy to generate heat may be dispersed. Each ofthe fine heating particles may have a diameter of about 1 nm to about100 μm so as to freely pass through the channel C having a depth ofabout 0.1 mm and a width of about 1 mm. When the electromagnetic energyis supplied to the fine heating particles through the laser beams, forexample, the temperature of the fine heating particles rises rapidly togenerate heat, and the fine heating particles are evenly dispersed inthe wax. The fine heating particles may have a core including a metalcomponent, and a hydrophobic surface structure. For example, the fineheating particle may have a molecular structure having a core formed ofFe and a plurality of surfactants surrounding Fe. The fine heatingparticles may be stored in carrier oil. The carrier oil may be alsohydrophobic so that the fine heating particles having the hydrophobicsurface structures may be evenly dispersed. The carrier oil, in whichthe fine heating particles are dispersed, is mixed with the melted phasetransition material, and the mixed material is loaded into the channel Cand coagulated to block the channel C. The fine heating particles arenot limited to the polymer particles described above, and may be quantumdots or magnetic beads. In addition, the fine heating particles may befine metal oxide materials, for example, Al₂O₃, TiO₂, Ta₂O₃, Fe₂O₃,Fe₃O₄, or HfO₂. On the other hand, the normally open valve does notnecessarily include the fine heating particles, and may be formed of thephase transition material without including the fine heating particles.

FIGS. 5A and 5B are cross-sectional views showing an example of thenormally open valve. The normally open valve includes a channel C, avalve chamber VC connecting to a part of the channel C, and a valvematerial V2 filled in the valve chamber VC. The valve material V2 may bethe same as the valve material V1 of the normally closed valve.Referring to FIG. 5A, before supplying the external energy to the valve,since the valve V2 exists in the valve chamber VC, and the channel Cmaintains an open state. Then, when the external energy is supplied tothe valve material V2, the valve material is melted and expanded to beinduced into the channel C, and the melted valve material V2 iscoagulated to block the flow of the fluid through the channel C.

FIG. 6 is an exploded perspective view of the microfluidic apparatus ofFIG. 1. Referring to FIG. 6, the platform 100 may include an upper plate110 and a partition plate 120. The microfluidic structure including thechambers and channels shown in FIGS. 1 and 2A through 2D is formed onthe partition plate 120. The chambers and channels formed on thepartition plate 120 have closed lower portions and open upper portions.When reaction cartridges 201 are coupled to mounting portions 202 formedon the partition plate 120 as shown in FIGS. 3A and 3B, the reactionchamber 200 is formed. However, one or more embodiments are not limitedto the above example, and the reaction chamber 200 may be formed bydirectly coating the surface of the mounting portion 202 with captureantibodies or antigens. In order to form the normally closed valve, thevalve material V1 may be loaded into the corresponding channel C asshown in FIG. 4A. In order to form the normally open valve, the valvematerial V2 may be loaded into the valve chamber VC connecting to thecorresponding channel C as shown in FIG. 5A.

A plurality of vent holes are formed in the upper plate 110 in order tomake the fluid flow smoothly through the chambers and channels includingthe first through fourth vent chambers 215, 225, 235, and 245. In FIG.6, the holes which are not denoted by reference numerals among the holesformed in the upper plate 110 denote the vent holes. Chambers facing thedetector (520 of FIG. 10), for example, the first through fourth QCchambers 35, 50, 60, and 70 and the detection chambers 250, are locatedat the same distances in the radial direction from the center C. Aprotective unit 112 for protecting a region 111 which corresponds to thefirst through fourth QC chambers 35, 50, 60, and 70 and the detectionchamber 250 may be formed on the upper plate 110. The protective unit112 protects the region 111 from contamination, or reduces the chance ofthe region 111 being contaminated while the microfluidic apparatus isbeing handled. For example, the protective unit 112 may include a firstrib 113 and a second rib 114 which protrude upward and surround theregion 111. The upper plate 110 may further include a third rib 115 thatprotrudes upward in order to represent an inlet 11 that is connected tothe sample chamber 10.

When the upper plate 110 is coupled to the partition plate 120, themicrofluidic structure formed on the partition plate 120 has the closedupper and lower portions, and the valves controlling the flow of fluidare formed on corresponding locations. Therefore, the microfluidicstructure, in which the fluid may be received and flow, is completed.The first, second, and third buffers and the washing buffer may beloaded into the first, second, and third buffer chambers 210, 220, and230 and the washing buffer chamber 240 on the partition plate 120,respectively, and the upper plate 110 is coupled to the partition plate120, and then, the microfluidic apparatus receiving the first, second,and third buffers and the washing buffer is fabricated. The upper plate110 may be coupled to the partition plate 120 using adhesion, radiofrequency welding, ultrasonic wave welding, laser welding, orultraviolet ray bonding process. Alternatively, after coupling the upperplate 110 to the partition plate 120, the first, second, and thirdbuffers and the washing buffer may be loaded into the first, second, andthird buffer chambers 210, 220, and 230 and the washing buffer chamber240 through inlets (not shown) formed in the upper plate 110 and theinlets may be blocked.

In order to form the normally closed valves and the normally openvalves, the valve materials may be loaded into the channels C and thevalve chambers VC, for example, through inlets (not shown) formed in theupper plate 110, after coupling the upper plate 110 to the partitionplate 120.

As another method of forming the normally closed valves and the normallyopen valves, the valve material is applied to a predetermined thicknesson locations where the valves will be formed on a lower surface 116 ofthe upper plate 110 as shown in FIG. 7. After that, the upper plate 110and the partition plate 120 are coupled to each other. In FIG. 7, tinyblack circles denote the valve material for forming the normally closedvalves, and black large circles denote the valve material for formingthe normally open valves. FIG. 8A is a cross-sectional view of a portionwhere the valve is formed after coupling the upper plate 110 to thepartition plate 120. Referring to FIG. 8A, since the valve material doesnot block the channel C, the normally open valve is formed when theupper plate 110 and the partition plate 120 are coupled to each other.In order to form the normally closed valve, the external energy isapplied to the tiny black circles to melt the valve material. Theexternal energy may be provided by the laser beam, for example. Then, asshown in FIG. 8B, the valve material is melted and coagulated whileblocking the channel C, and thus, the normally closed valve is formed.In order to open the closed valve, the energy that is similar to theenergy applied when the closed valve is formed, or a greater amount ofenergy, is applied to the valve material shown in FIG. 8B. Then, asshown in FIG. 8C, the valve material flows into the space in the channelC, and the channel C is opened. The processes of closing the channel Cby operating the open valve shown in FIG. 8A will be clarified byconsidering the processes of forming the closed valve shown in FIG. 8B.

An example of the microfluidic apparatus including the normally closedvalves and the normal open valves fabricated using the above describedprocesses, is shown in FIG. 8D. Referring to FIG. 8D, the normallyclosed valves are represented as small black circles, and the normallyopen valves are represented as large black circles. The microfluidicapparatus of FIG. 8D is different from the microfluidic apparatus ofFIG. 2A in that the normally open valves 206, 244, 265, and 272 arelocated in the channels that are to be closed. According to the abovestructure, there is no need to form the chambers (VC of FIG. 5A) forreceiving the valve material (V2 of FIG. 5A) for forming the normallyopen valves, and thus, the structure of the microfluidic apparatus issimplified.

In the above embodiment, a groove G for applying the valve material to apredetermined thickness is formed in the upper plate 110, and a steppedportion S corresponding to the groove G is formed in the channel C ofthe partition plate 120, however, one or more embodiments are notlimited to the above example. The groove G may not be formed on thebottom surface of the upper plate 110, and the stepped portion S may notbe formed in the channel C of the partition plate 120. Even when thegroove G and the stepped portion S are not formed, the normally openvalve and the normally closed valve may be formed by adjusting theamount of valve material and the energy intensity for melting the valvematerial. The groove G may be a reference for locating the positionwhere the valve material will be applied. The stepped portion S mayfacilitate flow of the melted valve material according to the capillaryphenomenon when the closed valve is opened.

FIG. 9 is a perspective view of the microfluidic apparatus fabricated byperforming the above described processes. Referring to FIG. 9, a barcode140 is disposed on a side portion of the platform 100. The barcode 140may be attached to the side portion of the platform 100. The barcode 140may include information about the fabrication data of the microfluidicapparatus, and a term of validity of the microfluidic apparatus. Inaddition, the barcode 140 may include data relating to a relationbetween the absorbance of the final resultant in the detection chamber250 and a concentration.

FIG. 10 is a diagram of a sample testing system using the microfluidicapparatus. Referring to FIG. 10, the system may include a rotationdriver 510, the detector 520, and an electromagnetic wave generator 530.The rotation driver 510 provides the microfluidic apparatus with acentrifugal force for centrifugating the sample and moving the fluid byrotating the microfluidic apparatus. The rotation driver 510 stops themicrofluidic apparatus at a predetermined location so that the valvesface the electromagnetic wave generator 530. The electromagnetic wavegenerator 530 operates the valves, and irradiates, for example, laserbeams. The electromagnetic wave generator 530 may move in a radialdirection of the microfluidic apparatus. In addition, the rotationdriver 510 rotates the microfluidic apparatus so that the chambers facethe detector 520 to detect the absorbance. The rotation driver 510 mayinclude a motor drive device (not shown) that may control an angularposition of the microfluidic apparatus. For example, the motor drivedevice may use a step motor or a direct current (DC) motor. The detector520 senses optical characteristics such as a fluorescent property, alight emission property, and/or an absorbing property of the materialthat is to be detected. A barcode reader 540 reads the barcode 140disposed on the side portion of the platform 100. The rotation driver510, the detector 520, the electromagnetic wave generator 530, and thebarcode reader 540 are located in a predetermined measuring chamber 550.A heater 560 is for maintaining a temperature in the measuring chamber550 as the appropriate temperature for performing the testing. Acontroller 570 is provided for controlling the sample analyzing process.

Hereinafter, a sample testing method using the above microfluidicapparatus will be described. In the present embodiment, processes ofdetecting certain protein from blood, as an example, will be described.

<Sample Loading>

In the microfluidic apparatus of the present embodiment, buffers and awashing buffer used in the testing operation are loaded in advance. Thatis, the first buffer chamber 210 receives a conjugate buffer forperforming the sandwich immunoassay. The second buffer chamber 220 mayreceive a substrate buffer which represents a predetermined color byperforming a substrate reaction with the resultant of the conjugatereaction. The third buffer chamber 230 may receive a stop solution forstopping the substrate reaction. The washing buffer chamber 240 receivesthe washing buffer. Therefore, for performing the sample test, wholeblood taken from a patient is loaded into the sample chamber 10 of themicrofluidic apparatus, and the microfluidic apparatus is mounted on therotation driver 510 to prepare for the sample test.

<Obtaining Barcode Information>

The information stored in the barcode 140 disposed on the side portionof the platform 100 is read using the barcode reader 540. It may beidentified whether the microfluidic apparatus is valid from theinformation about the fabrication data of the microfluidic apparatus andthe term of validity of the microfluidic apparatus stored in the barcode140. When the microfluidic apparatus is not in condition for performingthe valid test, the controller 570 may generate an alarm that informs auser that the microfluidic apparatus should be replaced. In addition,the information stored in the barcode 140 may include information aboutthe relation between the measured absorbance and a concentration of theprotein.

<Determining Whether Microfluidic Apparatus is Used>

An absorbance of the first QC chamber 35 disposed at an end portion ofthe sample separation unit 30 is measured using the detector 520. Whenthe measured absorbance represents that the blood exists in the first QCchamber 35, it implies that the microfluidic apparatus was previouslyused. In this case, the controller 570 may generate the alarm thatinforms the user that the microfluidic apparatus should be replaced.

<Temperature Detection>

An absorbance of the fourth QC chamber 70 is measured using the detector520. Since the thyon dye, the absorbance of which varies depending onthe temperature, is accommodated into the fourth QC chamber 70, thetemperature of the microfluidic apparatus may be checked using theabsorbance of the fourth QC chamber 70. The microfluidic apparatus maybe stored in cold storage at a temperature of about 4° C. in order tomaintain activities of the first through third buffers in a state wherethe first through third buffers and the washing buffer are loaded intothe microfluidic apparatus. Since the microfluidic apparatus that iskept cold cannot be used directly in the test, when the temperature ofthe microfluidic apparatus does not reach the appropriate temperature,for example, 20° C., the controller 570 drives the heater 560 to raisethe temperature of the measuring chamber 550. After that, the processesof measuring the absorbance of the fourth QC chamber 70 and detectingthe temperature of the microfluidic apparatus are repeated, and then,the test may be performed when the temperature reaches the appropriatetemperature for performing the test. The number of repetitions may beset appropriately, and when the temperature does not reach theappropriate temperature even if the predetermined number of repetitionsis performed, the controller 570 may generate an error message.

<Determining Whether an Amount of Sample is Appropriate>

The microfluidic apparatus is rotated at a low speed to convey the bloodfrom the sample chamber 10 to the sample separation unit 30. The lowspeed is a rotation speed generating the centrifugal force that issuitable for conveying the fluid. After filling the sample separationunit 30, the blood is conveyed to the second QC chamber 50 through thechannel 51. The detector 520 measures the absorbance of the second QCchamber 50. The absorbance varies depending on the amount of blood inthe second QC chamber 50. When it is determined that the amount of bloodis not sufficient from the absorbance of the second QC chamber 50, thecontroller 570 may generate an alarm which informs the user that moreblood should be loaded into the sample chamber 10.

<Centrifugating Sample>

The rotation driver 510 rotates the microfluidic apparatus at a highspeed. Here, the high rotation speed may divide the blood into bloodserum or blood plasma, that is, the supernatant, and blood cells, thatis, the precipitate. Then, the blood cells are moved to the precipitatecollecting unit 32, and the supernatant remains in the supernatantcollecting unit 31.

<Metering Supernatant>

The electromagnetic wave generator 530 irradiates the electromagneticwaves to the normally closed valve 33. Then, the valve material ismelted and the valve 33 is opened as shown in FIG. 4B or 8C. Therotation driver 510 rotates the microfluidic apparatus to generate thecentrifugal force. Then, the supernatant is moved to the supernatantmetering chamber 40 from the supernatant collecting unit 31 through thechannel 34. Since the valve 41 located at the outlet of the supernatantmetering chamber 40 is normally closed, the supernatant fills thesupernatant metering chamber 40. Therefore, when the amount of thesupernatant is sufficient, the supernatant, the volume of which equalsthe volume of the supernatant metering chamber 40, is received in thesupernatant metering chamber 40.

<Determining Quantity and Quality of Supernatant>

The valve 62 located in the inlet of the channel 61 is opened using theelectromagnetic wave generator 530. When the microfluidic apparatus isrotated, the supernatant is induced into the third QC chamber 60 throughthe channel by the centrifugal force. The absorbance of the third QCchamber 60 is measured using the detector 520. When the measuredabsorbance is the reference absorbance, which indicates that asufficient amount of supernatant is in the third QC chamber 60, it isdetermined that a sufficient amount of supernatant is received in thesupernatant metering chamber 40. When the measured absorbance is greaterthan the reference absorbance, the supernatant may include impuritiesbecause the centrifugation of the sample is not performed properly orthe sample is defective. In this case, the controller 570 may generatean alarm which informs the user that the microfluidic apparatus shouldbe replaced and the test should be performed again. In addition, whenthe absorbance is less than the reference absorbance or greater than thereference absorbance, it may mean that the amount of supernatantreceived in the third QC chamber 60 is insufficient or the supernatantincludes air pores. In this case, the amount received in the supernatantmetering chamber 40 is insufficient. Therefore, the controller 570 maygenerate an alarm which informs the user that the microfluidic apparatusshould be replaced and the test should be performed again.

<Determining Operation Error of the Valve 33>

When the absorbance of the third QC chamber 60 represents that the thirdQC chamber 60 is empty, it may mean that the valve 33 does not operateproperly and the supernatant does not move to the supernatant meteringchamber 40 and the third QC chamber 60. In this case, the valve 33 isdriven using the electromagnetic wave generator 530 and the absorbanceof the third QC chamber 60 may be measured again. When the same resultis shown in the re-measuring process, the controller 570 indicates theoperation error of the valve 33 and may generate an alarm which informsthe user that the microfluidic apparatus should be replaced.

<Re-Detection of Temperature>

Before performing a process for detecting a specimen, the temperature ofthe microfluidic apparatus may be measured again. The antigen-antibodyreaction for detecting the specimen may be performed well in a certaintemperature range. For example, the antigen-antibody reaction fordetecting the specimen from the bio-sample such as blood may beperformed at a temperature of about 37° C. Therefore, the detector 520may detect the absorbance of the fourth QC chamber 70 again to measurethe temperature. When the temperature does not reach the temperature ofabout 37° C., the controller 570 drives the heater 560 to raise thetemperature of the measuring chamber 550. After that, the process ofdetecting the absorbance of the fourth QC chamber 70 to measure thetemperature of the microfluidic apparatus is repeated. When thetemperature of the microfluidic apparatus reaches the temperature ofabout 37° C., the test may be continued. The number of times thetemperature is re-measured may be set appropriately. If the temperatureof the microfluidic apparatus is lower than 37° C. even when thetemperature is measured again, the controller 570 may generate atemperature error message and terminate the test. Alternatively, thecontroller 570 may generate an alarm which informs the user that themicrofluidic apparatus should be replaced.

<Performing Antigen-Antibody Reaction>

The valve 41 located at the outlet of the supernatant metering chamber40 is opened using the electromagnetic wave generator 530. When themicrofluidic apparatus is rotated, the supernatant received in thesupernatant metering chamber 40 is moved to the reaction chamber 200through the channel 42 due to the centrifugal force.

The valves 212 and 213 are opened using the electromagnetic wavegenerator 530. Then, the conjugate buffer is moved from the first bufferchamber 210 to the first metering chamber 211. Since the first bufferchamber 210 communicates with the external air via the valve 212 and thefirst vent chamber 215, the conjugate buffer may be easily moved to thefirst metering chamber 211. Since the valve 214 located at the outlet ofthe first metering chamber 211 is the normally closed valve, theconjugate buffer fills the first metering chamber 211 first. After that,excessive conjugate buffer is received in the first excessive bufferchamber 229. When the valve 214 located at the outlet of the firstmetering chamber 211 is opened using the electromagnetic wave generator530, a fixed amount of conjugate buffer is moved to the reaction chamber200.

In order to mix the supernatant with the conjugate buffer, the rotationdriver 510 may perform a shaking operation of the microfluidic apparatusa few times. In the reaction chamber 200, a binding reaction among thespecimen, the captured antibody, and secondary antibody included in theconjugate buffer is performed. After that, the valve 205 that is locatedon the outlet, which is located on a side of the first waste chamber260, of the reaction chamber 200 is opened using the electromagneticwave generator 530. The impurities except for the specimen captured bythe capture antibody and the secondary antibody are moved to the firstwaste chamber 260 through the end portion 261 and the final end 262 ofthe first waste channel 264. After that, when the electromagnetic wavesare irradiated onto the normally open valve 265 located at the final end262 of the first waste channel 264, the valve material is melted andcoagulated to close the valve 265 as shown in FIG. 5B or FIG. 8B. Sincethe normally open valve 265 located at the final end 262 of the firstwaste channel 264 is closed and the valve 266 located at the final end263 is closed, and the reaction chamber 200 and the first waste chamber260 are isolated from each other.

<Washing>

The valves 242 and 243 are opened using the electromagnetic wavegenerator 530. Then, the washing buffer is moved from the washing bufferchamber 240 to the reaction chamber 200. Since the washing bufferchamber 240 communicates with the external air via the valve 242 and thefourth vent chamber 245, the washing buffer may be easily moved to thereaction chamber 200. For performing the washing operation, the rotationdriver 510 may perform a shaking operation of the microfluidic apparatusa few times. The valve 266 is opened using the electromagnetic wavegenerator 530. Then, the washing buffer in the reaction chamber 200 ismoved to the first waste chamber 260 through the end portion 261 and thefinal end 263 of the first waste channel 264 with the reactionimpurities. The normally open valve 206 located at the end portion 261of the first waste channel 264 is closed using the electromagnetic wavegenerator 530. Accordingly, the reaction chamber 200 and the first wastechamber 260 are isolated from each other again.

<Obtaining Reference Absorbance>

Since the blank chamber 241 is connected to the washing buffer chamber240 through the normally open valve 244, the washing buffer is alsoreceived in the blank chamber 241. The valve 246 located at the outletof the blank chamber 241 is opened using the electromagnetic wavegenerator 530. When the microfluidic apparatus is rotated, the washingchamber received in the blank chamber 241 is moved to the detectionchamber 250. Since the blank chamber 241 is in communication with theexternal air via the open valve 244, the washing buffer chamber 240, thevalve 242 that is opened in advance, and the fourth vent chamber 245,the washing buffer may be easily moved to the detection chamber 250. Thedetector 520 measures the absorbance of the detection chamber 250. Themeasured absorbance becomes the reference absorbance representing thestate of the detection chamber 250. The valve 251 located at the outletof the detection chamber 250 is opened using the electromagnetic wavegenerator 530. Then, the washing buffer is moved from the detectionchamber 250 to the second waste chamber 270 through the second wastechannel 271. After that, the open valve 272 located at the inlet of thesecond waste chamber 270 is closed using the electromagnetic wavegenerator 530. Accordingly, the detection chamber 250 and the secondwaste chamber 270 are isolated from each other. In addition, the openvalve 244 located at the inlet of the blank chamber 241 is closed usingthe electromagnetic wave generator 530. Therefore, the detection chamber250 and the blank chamber 241 are isolated from each other.

<Determining the Wrong Operation of the Valve 246>

If the absorbance represents the empty state of the detection chamber250 during the process of obtaining the reference absorbance, it maymean that the valve 246 does not operate properly. In this case, theprocess of obtaining the reference absorbance may be repeated. When thesame error is repeatedly generated, the controller 570 may generate analarm which informs the user that the microfluidic apparatus should bereplaced. The number of repetitions may be set appropriately.

<Substrate Reaction>

The valves 222 and 223 are opened using the electromagnetic wavegenerator 530. Then, the substrate buffer is moved from the secondbuffer chamber 220 to the second metering chamber 221. Since the secondbuffer chamber 220 is in communication with the external air via thevalve 222 and the second vent chamber 225, the substrate buffer may beeasily moved to the second metering chamber 221. Since the valve 224located at the outlet of the second metering chamber 221 is closed, thesubstrate buffer fills the second metering chamber 221 first. Theexcessive substrate buffer is received in the first excess bufferchamber 229. When the closed valve 224 located at the outlet of thesecond metering chamber 221 is opened using the electromagnetic wavegenerator 530, the weighed amount of the substrate buffer is moved tothe reaction chamber 200. The rotation driver 510 may perform a shakingoperation of the microfluidic apparatus a few times in order to mix thesubstrate buffer with the resultant of the antigen-antibody reaction inthe reaction chamber 200. Due to the substrate reaction, the mixture inthe reaction chamber 200 has the color corresponding to the amount ofthe specimen.

<Reaction Stop>

The valves 232 and 233 are opened using the electromagnetic wavegenerator 530. Then, the stop buffer is moved from the third bufferchamber 230 to the third metering chamber 231. Since the third bufferchamber 230 is in communication with the external air via the valve 232and the third vent chamber 235, the stop buffer may be easily moved tothe third metering chamber 231. Since the valve 234 located at theoutlet of the third metering chamber 231 is the closed valve, the stopbuffer fills the third metering chamber 231 first. After that, theexcessive stop buffer is received in the second excess buffer chamber239. When the valve 244 located at the outlet of the third meteringchamber 231 is opened using the electromagnetic wave generator 530, themetered amount of stop buffer is moved to the reaction chamber 200. Inorder to mix the stop buffer with the resultant of the antigen-antibodyreaction in the reaction chamber 200 and the substrate buffer, therotation driver 510 may perform a shaking operation of the microfluidicapparatus a few times. The substrate reaction is suspended by the stopbuffer.

<Detecting Concentration of Specimen>

The closed valve 207 located at the outlet, which is located at a sideof the detection chamber 250, of the reaction chamber 200 is openedusing the electromagnetic wave generator 530. Then, the final fluid ismoved to the detection chamber 250. The absorbance of the detectionchamber 250 is measured using the detector 520. At this time, theabsorbance is measured a few times at predetermined time intervals inorder to obtain the final absorbance which does not change. Thecontroller 570 calculates the concentration of the specimen by using thedifference between the obtained absorbance and the reference absorbance,from the information relating to the concentration of protein accordingto the absorbance stored in the barcode 140.

It should be understood that the exemplary embodiments described hereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments.

1. A microfluidic apparatus comprising: a sample chamber comprising aninlet and a receiving portion, wherein a backflow prevention unit isdisposed in the receiving portion; a sample separation unit whichreceives a sample from the sample chamber and separates a supernatantfrom the sample using a centrifugal force; a buffer chamber whichreceives a reaction buffer; a washing buffer chamber which receives awashing buffer; a reaction chamber which is connected to and receivesthe supernatant from the sample separation unit, is connected to andreceives the reaction buffer from the buffer chamber, is connected toand receives the washing buffer from the washing buffer chamber, and iscoated with capture antibodies or antigens for capturing a specimen; asupernatant metering chamber which is disposed between the sampleseparation unit and the reaction chamber to meter an amount of thesupernatant; and a detection chamber which is connected to the reactionchamber, receives a final reaction material from the reaction chamber,and has a space in which absorbance is measured for testing a specimenof the final reaction material.
 2. The microfluidic apparatus of claim1, wherein the reaction chamber comprises a reaction cartridge on whichthe capture antibodies or antigens are coated.
 3. The microfluidicapparatus of claim 1, further comprising: a first waste chamber whichreceives impurities discarded from the reaction chamber; a first wastechannel which connects the reaction chamber to the first waste chamber,and includes an end portion that is connected to the reaction chamber,and two final ends that diverge from the end portion and are connectedto the first waste chamber; and first and second normally closed valvesand first and second normally open values, wherein the first normallyclosed valve and the first normally open valve are disposed in the endportion of the first waste channel, and the second normally open valveand the second normally closed valve are respectively disposed in thetwo final ends of the first waste channel so that the reaction chamberand the first waste chamber are isolated from each other afterdiscarding the impurities from the reaction chamber.
 4. The microfluidicapparatus of claim 3, further comprising: a blank chamber which isconnected to the washing buffer chamber and the detection chamber,receives the washing buffer from the washing chamber, and provides thewashing buffer to the detection chamber in order to measure a referenceabsorbance; a second waste chamber which receives the washing bufferdiscarded from the detection chamber; a second waste channel whichconnects the detection chamber to the second waste chamber; and anormally closed valve and a normally open valve which are disposed inthe second waste channel so that the detection chamber and the secondwaste chamber are isolated from each other after discarding the washingbuffer.
 5. The microfluidic apparatus of claim 1, wherein the bufferchamber comprises: a first buffer chamber which receives one of aconjugate buffer for performing a sandwich immunoassay reaction and acompetitive protein for performing a competitive immunoassay reaction; asecond buffer chamber which receives a substrate buffer that indicates apredetermined color due to a substrate reaction with a resultant of aconjugate reaction or the competitive immunoassay reaction; and a thirdbuffer chamber which receives a stop buffer that stops the substratereaction.
 6. The microfluidic apparatus of claim 1, further comprising:a vent chamber which forms a vent path which allows the buffer chamberto access external air; a first normally closed valve which is disposedbetween the buffer chamber and the vent chamber; and a second normallyclosed valve which is disposed at an outlet of the buffer chamber. 7.The microfluidic apparatus of claim 1, further comprising: a buffermetering chamber which meters reaction buffer between the buffer chamberand the reaction chamber; and an excess buffer chamber which receivesfrom buffer metering chamber a portion of the reaction buffer exceedinga capacity of the buffer metering chamber.
 8. The microfluidic apparatusof claim 1, further comprising: a vent chamber which forms a vent pathwhich allows the washing buffer chamber to access external air; a firstnormally closed valve which disposed is between the washing bufferchamber and the vent chamber; and a second normally closed valve whichis disposed at an outlet of the washing buffer chamber.
 9. Themicrofluidic apparatus of claim 1, further comprising a first qualitycontrol chamber which is disposed at an end of the sample separationunit for identifying whether the microfluidic apparatus has beenpreviously used by detecting absorbance.
 10. The microfluidic apparatusof claim 9, further comprising a second quality control chamber which isconnected to the sample separation unit and receives a portion of thesample exceeding a capacity of the sample separation unit.
 11. Themicrofluidic apparatus of claim 10, further comprising a third qualitycontrol chamber which detects an absorbance of the supernatant, and isconnected to a channel that connects the reaction chamber to the sampleseparation unit to receive the supernatant from the sample separationunit.
 12. The microfluidic apparatus of claim 11, further comprising afourth chamber which receives a material having an absorbance whichvaries depending on temperature.
 13. The microfluidic apparatus of claim1, further comprising a rotatable platform in which the sample chamber,the sample separation unit, the buffer chamber, the washing bufferchamber, the reaction chamber and the detection chamber are formed,wherein the platform comprises: a partition plate, on which an engravedstructure providing spaces for receiving a fluid and for formingchannels through which the fluid flows and having an opened upperportion is formed, and an upper plate coupled to the upper portion ofthe partition plate to block the upper portion of the engravedstructure.
 14. The microfluidic apparatus of claim 4, wherein the valvesinclude a valve material that is melted by electromagnetic wave energy.15. The microfluidic apparatus of claim 14, wherein the valve materialis a phase transition material, a phase of which is changed by theelectromagnetic wave energy, or a thermosetting resin.
 16. Themicrofluidic apparatus of claim 15, wherein the valve material comprisesheating particles dispersed in the phase transition material to generateheat by absorbing the electromagnetic wave energy.
 17. The microfluidicapparatus of claim 1, wherein the backflow prevention unit comprises oneor more ribs disposed in a direction crossing a flowing direction of thesample.
 18. The microfluidic apparatus of claim 1, wherein the samplechamber further comprises a first side wall and a second side wall, thefirst side wall is farther from a center of rotation than the secondside wall, and a distance from the center of rotation to the first sidewall increases from the inlet to an outlet.